Polysiloxane graft copolymers, flexible coating compositions comprising same and branched polysiloxane macromers for preparing same

ABSTRACT

Hydroxy functional polysiloxane graft copolymers are provided. The copolymer is crosslinkable by hydroxy-reactive crosslinking agent and, in particular, is suitable for use in thermosetting coating compositions adapted to form a flexible cured coating over a variety of substrates, such as metal and plastic. The copolymer has a number average molecular weight between about 1000 and about 15,000, has a hydroxyl number between about 30 and about 300, and is the reaction product of carbon-carbon double bond-reactive monoethylenically unsaturated monomer with hydroxy functional carbon-carbon double bond-bearing branched polysiloxane macromer. The macromer is the reaction product of (i) epoxy monomer having the formula: ##STR1## with (ii) hydroxy functional polysiloxane reactant containing 0-10 urethane linkages per molecule.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of Ser. No. 816,485 filedJan. 6, 1986 now U.S. Pat. No. 4,673,718

TECHNICAL FIELD

This invention relates to resins and flexible coating compositionscomprising same which have excellent adherence to metal and plastic andpossess superior weathering properties. More particularly, the inventionrelates to hydroxy functional polysiloxane graft copolymers and tocoating compositions comprising same.

BACKGROUND

Recently, there has been interest in the use of resilient coatingmaterials for areas which are subject to mechanical shock, such asautomobile bumpers, moldings and front ends. To maintain the desiredappearance for a protective coating on a motor vehicle body panel orlike application, any such coating must have certain properties, such asa high degree of extensibility, impact resistance, and resistance tocracking and degradation under severe environmental conditions such aslow temperature and high humidity. Conventional coatings, includingthose heretofore employed on rubber and similar extensible objects, donot have the required combination of properties. Generally, compositionsthat are flexible enough to be applied over both metal and plasticsubstrates have rather poor weatherability, appearance, and/or overalldurability.

U.S. Pat. No. 3,882,189 and U.S. Pat. No. 3,962,522 are exemplary ofnumerous patents which describe flexible coating compositions, whereinthe resin comprises polyurethane modified polyesters formed by reactingpolyisocyanate with polyester polyols. These resins are cured withamine-aldehyde crosslinkers. It is taught therein, that the presence ofthe urethane groups in the polymer significantly contributes to theflexibility as well as improved weathering properties, gloss, andabrasion resistance of the coating. Such coatings, however, are not ofan overall quality to meet certain applications, particularly automotiveapplications. Accordingly, it is an object of the present invention toprovide novel polysiloxane graft copolymers and solvent based,thermosetting coating compositions comprising same, suitable to produceflexible cured coatings with good adhesion over diverse substratesincluding metal and plastic. In this regard, it is a particular objectof the invention to provide such flexible coating compositions atsufficiently low Volatile Organic Content (VOC) to aid in meetinggovernmental emissions guidelines and yet which can be applied to asubstrate by spraying or other known methods. It is another object ofthe invention to provide a composition which will form a coating on asubstrate, which coating has advantageous physical properties including,for example, humidity and solvent resistance, flexibility and corrosionprotection for the underlying substrate.

Additional aspects and advantages of the invention will be apparent fromthe following description thereof.

DISCLOSURE OF THE INVENTION

According to the present invention, a novel, non-gelled, hydroxyfunctional polysiloxane graft copolymer is provided. The copolymer iscrosslinkable by hydroxy-reactive crosslinking agent and, in particular,is suitable for use in thermosetting coating compositions adapted toform a flexible cured coating over a variety of substrates, such asmetal and plastic. The copolymer of the invention has a number averagemolecular weight between about 1000 and about 15,000, has a hydroxylnumber between about 30 and about 300, and is the reaction product ofcarbon-carbon double bond-reactive monoethylenically unsaturated monomerwith hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer. This reaction is performed under free radicalpolymerization reaction conditions and the monomer bears substantiallyno functionality which would be substantially reactive with the hydroxyfunctionality of the macromer under such reaction conditions. Themacromer is the reaction product of (i) epoxy monomer having theformula: ##STR2## where R preferably is H or alkyl of 1 to about 7carbons and R' is a hydrocarbon linking moiety, preferably alkyl orCOO(CH₂)_(n), n being 0 to about 7, with (ii) hydroxy functionalpolysiloxane reactant containing 0-10 urethane linkages per molecule.

According to the coating composition aspect of the invention, theaforesaid copolymer is employed with polyfunctional, hydroxy-reactivecrosslinking agent selected from aminoplast crosslinking agent,polyisocyanate crosslinking agent, blocked polyisocyanate crosslinkingagent comprising at least two isocyanate groups blocked by reaction withactive hydrogen bearing blocking agent, and any compatible mixturethereof. The crosslinking agent is included in an amount sufficient toprovide, at a cure temperature of the composition, between about 0.5 andabout 1.5 hydroxy-reactive groups per hydroxy group contributed by thehydroxy functional polysiloxane graft copolymer.

The coating compositions of the invention can be formulated as eitherone component coating compositions or two component coatingcompositions. Typically, unblocked polyisocyanate crosslinking agent isemployed in two component compositions in view of its reactivity. Acomposition of the invention can be formulated, for example, as a onecomponent primer, typically employing blocked polyisocyanate oraminoplast crosslinking agent, as a one component topcoat, preferablyemploying aminoplast crosslinking agent, or as a two component coating,typically employing polyisocyanate crosslinking agent. Also, the graftcopolymer of the invention can be formulated as a pigmented base coat,typically a one component composition, for a base coat/clear coat systemsuch as are known for use as automotive finishes. It also can beformulated as the clear coat thereof, either as a one component or a twocomponent composition.

Advantageously, the flexible coatings of the invention possess superiorweathering properties as well as excellent adhesion to metal andplastic, thus making them well suited for use as coatings on, forexample, various motor vehicle components. The ability to use the samecoating composition on metal and plastic components in motor vehicleproduction offers distinct commercial advantages, particular in terms ofproduction efficiency. Additionally, because these coatings can beemployed on metal as well as plastic components, the problem of colormatching, which must be resolved when using different coatings on metaland plastic parts which are to be in proximity to one another, iseliminated. The siloxane moieties incorporated into the graft copolymeradvantageously provide enhanced flexability, durability andweatherability and provide lowe viscosity for high solids coatings.These and additional features and advantages of the invention will bebetter understood in view of the following detailed disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The resin of the invention is a novel, hydroxy functional polysiloxanegraft copolymer of number average molecular weight (M_(n)) between about1,000 and about 15,000, preferably between about 1,000 and about 4,000,and having a hydroxyl number between about 30 and about 300, preferablybetween about 50 and about 150. The resin is optionallyurethane-modified, more specifically, containing about 0-10 urethanelinkages per molecule. Preferably, the resin contains about 0-5 urethanelinkages per molecule. As disclosed above, the resin is the reactionproduct of carbon-carbon double bond-reactive monoethylenicallyunsaturated monomer with certain hydroxy functional carbon-carbon doublebond-bearing branched polysiloxane macromer. Each of these reactants isdiscussed below in greater detail.

Carbon-Carbon Double Bond-Reactive Monoethylinically Unsaturated Monomer

Numerous carbon-carbon double bond-reactive monoethylenicallyunsaturated monomers suitable for making the graft copolymer are knownto the skilled of the art. Included are many which are commerciallyavailable and many which will be readily apparent in view of the presentdisclosure. The choice of monomer reactant employed in making the graftcopolymer will depend to a large extent upon the particular applicationintended for the resin or for the coating composition in which the resinis to be used. Examples of suitable monoethylenically unsaturatedmonomers include, for example, vinyl aromatic hydrocarbons such asstyrene, alpha methyl styrene, and vinyl toluene, vinyl acetate, vinylchloride, and the like.

Preferred monomers are acrylate monomers. Numerous suitable acrylatemonomers are known to the skilled of the art and include many which arecommercially available and which will be readily apparent in view of thepresent disclosure. As noted above, the choice of monomer reactantemployed in preparing the resin of the invention will depend to a largeextent upon the particular application intended for the resin or for thecomposition in which the resin is used. Suitable hydroxy-substitutedalkyl(meth)acrylates (where "alkyl(meth)acrylates" means, in thealternative, alkylacrylates and alkylmethacrylates) which can beemployed comprise members selected from the group consisting of thefollowing esters of acrylic or methacrylic acid and C2-C12 aliphaticglycols: 2-hydroxy ethyl acrylate; 3-chloro-2-hydroxypropyl acrylate;2-hydroxy-1-methylethyl acrylate; 2-hydroxypropyl acrylate;3-hydroxypropyl acrylate; 2,3-dihydroxypropyl acrylate; 2-hydroxybutylacrylate; 4-hydroxybutyl acrylate; diethyleneglycol acrylate;5-hydroxypentyl acrylate; 6-hydroxyhexyl acrylate; triethyleneglycolacrylate; 7-hydroxyheptyl acrylate; 2-hydroxy-1-methylethylmethacrylate; 2-hydroxypropyl methacrylate; 3-hydroxypropylmethacrylate; 2,3-dihydroxypropyl methacrylate; 2-hydroxybutylmethacrylate; 4-hydroxybutyl methacrylate; 3,4-dihydroxybutylmethacrylate; 5-hydroxypentyl methacrylate; 6-hydroxyhexyl methacrylate;1,3-dimethyl-3-hydroxybutyl methacrylate; 5,6-dihydroxyhexylmethacrylate; and 7-hydroxyheptyl methacrylate. Although one of ordinaryskill in the art will recognize that many different hydroxy-substitutedalkyl(meth)acrylates including those listed above could be employed, thepreferred hydroxy functional monomers for use in the resin of thisinvention are hydroxy-substituted alkyl acrylates and methacrylateshaving a total of 5 to 7 carbon atoms, i.e., esters of C2-C3 dihydricalcohols and acrylic or methacrylic acids, such as hydroxyethylmethacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate andhydroxypropyl acrylate,

Most preferably, the hydroxy-substituted alkyl(meth)acrylate monomercomprises a compound of the formula: ##STR3## wherein R¹ is hydrogen ormethyl and R² and R³ are independently selected from the groupconsisting of hydrogen and alkyl of from 1 to 6 carbon atoms.Illustrative of these particularly suitable hydroxy-substitutedalkyl(meth)acrylate monomers are 2-hydroxyethyl methacrylate,2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutylacrylate and 2-hydroxy-1-methylhexyl acrylate.

Suitable non-hydroxy substituted alkyl(meth)acrylate monomers which maybe employed are (meth)acrylates (as before, meaning esters of eitheracrylic or methacrylic acids) as well as mixtures of acrylates and vinylhydrocarbons. Preferred non-hydroxy substituted monomers are esters ofC1-C12 monohydric alcohols and acrylic or methacrylic acids, e.g.,methylmethacrylate, ethylacrylate, butylacrylate, butyl-methacrylate,hexylacrylate, 2-ethylhexylacrylate, lauryl-methacrylate, glycidylmethacrylate, and the like.

Particularly preferred non-hydroxy substituted monomers are compoundsselected from the group consisting of monomers of the formula: ##STR4##wherein R⁴ is alkyl of from 1 to 6 carbon atoms and R⁵ is hydrogen ormethyl. Particularly preferred are butyl acrylate, butyl methacrylateand methyl methacrylate.

The aforesaid monovinyl aromatic hydrocarbons, preferably containingfrom 8 to 12 carbon atoms, including styrene, alpha-methyl styrene,vinyl toluene, t-butyl styrene, chlorostyrene and the like, whenemployed, will generally be present in an amount of from about 5 to 95weight percent, preferably from about 5 to 25 weight percent of thetotal monoethylenically unsaturated monomer.

In addition, other suitable monoethylenically unsaturated monomers suchas vinyl chloride, acrylonitrile, methacrylonitrile, vinyl acetate,acrylic acid and methacrylic acid also may be employed. In the case ofacrylic acid, when employed, this monomer will generally be present inan amount from about 2 to 5 weight percent of the total monomer mixture.The remaining above-mentioned monomers will generally be used in anamount of from 3 to 10 weight percent of the monomer mixture, whenemployed.

Hydroxy Functional Carbon-Carbon Double Bond-Bearing BranchedPolysiloxane Macromer

The hydroxy functional polysiloxane macromer is reacted with the abovedescribed monoethylenically unsaturated monomer according to any ofvarious methods well known to the skilled of the art, which methods willbe apparent in view of the present disclosure. Specifically, themacromer and the monomer are employed in a weight ratio of from about90:10 to about 40:60, more preferably from about 75:25 to about 50:50,respectively. Preferably, all double bonds of the macromer are reactedwith monomer double bonds. It will be apparent that the resulting resinwill be hydroxy functional by virtue of the macromer hydroxyl groups andthe monomer hydroxyl groups (if any). Suitable reaction conditions willbe apparent to the skilled of the art and, generally, will include asolvent system and reaction temperature favoring free radicalpolymerization reaction.

The hydroxy functional polysiloxane macromer is the reaction product ofany of certain epoxy acrylate with any of certain hydroxy functionalpolysiloxane reactants. Each of these reactants is discussed below ingreater detail.

Epoxy Monomer

Epoxy monomer reactants suitable for reaction with hydroxy functionalpolysiloxane reactants in making the macromer of the invention are thoseaccording to the formula: ##STR5## wherein R preferably is hydrogen oralkyl of 1 to about 7 carbons and R' is a hydrocarbon linking moiety.preferably alkyl or COO(CH₂) n being 0 to about 7. Numerous such epoxymonomers are well known to the skilled of the art and include many whichare commercially available or readily prepared according to knownmethods. The choice of epoxy monomer employed in preparing the macromerwill depend largely upon the particular application intended for thefinal resin or composition comprising the resin. Preferred epoxy monomerinclude, for example, glycidyl acrylate, glycidyl methacrylate and amixture thereof. Hydroxy Functional Polysiloxane Reactant

The hydroxy functional polysiloxane reactant has a number averagemolecular weight (M_(n)) preferably between about 1,000 and about12,000, more preferably between about 1,000 and about 3,000, and has ahydroxyl number preferably between about 30 and about 300, morepreferably between about 50 and about 150. As discussed further below,this polysiloxane reactant preferably, but not necessarily, is urethanemodified, that is, bears urethane linkages in the polysiloxane backbone.Suitable hydroxy functional polysiloxane reactants, both urethanemodified and unmodified, will be apparent in view of the presentdisclosure and can be prepared according to known methods which alsowill be apparent in view of the present disclosure. The choice ofpolysiloxane reactant will depend to a large extent upon the particularapplication intended for the final resin or composition in which suchresin is used.

The epoxy acrylate reactant and polysiloxane reactant are reactedtogether according to known methods and reaction conditions. Typically,these two reactants are employed in molar ratio of from about 2:1 toabout 1:2, more preferably about 1:1. More generally, the epoxy acrylateis used in an amount insufficient to yield a gelled reaction product.Also, the epoxy acrylate reactant is used in an amount insufficient toreact with all of the hydroxy functionality of the polysiloxane, sincethe reaction product, the branched polysiloxane macromer, must havehydroxy functionality to react with the crosslinking agent during cure.In preparing the macromer a catalyst should be employed for the reactionbetween the epoxy functionality of the epoxy acrylate and the hydroxyfunctionality of the polysiloxane. Suitable catalysts for this reactionare known and include commercially available catalysts, such as sulfonicacid catalyst, for example CG 21-746 (trademark) available from CibaGeigy Corp., Ardsley, N.Y., and phosphine catalyst, for example Shell1201 (trademark; Shell Chemical Co.). Additional suitable catalysts willbe apparent in view of the present disclosure. It is also preferred toemploy an agent to inhibit polymerization reaction of the carbon-carbondouble bonds of the epoxy acrylate reactant. Suitable inhibiting agentsare well known and include, for example, hydroquinone and others whichwill be apparent in view of this disclosure.

One suitable class of polysiloxane reactants comprises the reactionproducts of first reactant comprising polyol with second reactantcomprising certain alkoxy silicone and, optionally, dicarboxylic acid oran anhydride thereof. Where the graft copolymer is to be employed in ahigh solids coating for motor vehicle exterior body panels, for example,such second reactant preferably comprises about 5%-35% by weight alkoxysilicone and the remainder dicarboxylic acid or anhydride; morepreferably the second reactant comprises about 5%-15% alkoxy silicone.Obviously, where the second reactant comprises dicarboxylic acid oranhydride, the reaction product of the second reactant with polyol willcontain polyester linkages as well as polysiloxane linkages. Herein,such reaction product will be referred to simply as polysiloxaneregardless whether it has such polyester linkages. The alkoxy siliconecan be reacted with polyol either simultaneously with the dicarboxylicacid or sequentially (in either order) and the alkoxy silicone anddiacid also can be reacted with separate portions of the polyol. Mostpreferably the polysiloxane is an oligomeric polysiloxane.

Preferably, the diacid is selected from the group consisting ofsaturated and unsaturated, cyclic and acyclic aliphatic dicarboxylicacids, aromatic dicarboxylic acids, and suitable anhydrides thereof.Preferred dicarboxylic acids are the C₆ -C₃₆ acids, which include, forexample, adipic, azelaic, sebasic, dodecane dicarboxylic acid,cyclohexanedicarboxylic acid and dimer acids. More preferably, thedicarboxylic acids employed are aliphatic dicarboxylic acids, mostpreferably additionally being linear, for example, adipic, azelaic,dimer, and dodecanoic. Also suitable for use are blocked dicarboxylicacids such as dimethyl-1,4-cyclohexanedicarboxylate. Mixtures ofsuitable diacids and/or their anhydrides may also be used as thedicarboxylic acid component in this invention.

Numerous suitable alkoxy silicones for use in making the hydroxyfunctional polysiloxane reactant are known to the skilled of the art andwill be readily apparent in view of the present disclosure. Included aremany commercially available alkoxy silicones and others which can bereadily prepared according to known methods. Preferred alkoxy siliconeshave number average molecular weight between about 350 and about 10,000,more preferably between about 350 and about 1000. Preferred are those ofthe general formula: ##STR6## wherein each Q is independently selectedfrom hydrogen, alkyl, alkoxy, aryl, aryloxy and the like, each alkylmoiety preferably being C₁ to C₇ and each arly moiety preferably beingC₆ -C₈ ; each Q' is independently selected from alkyl, preferably C₁ toC₇ alkyl; and n is 1 to about 75, preferably about 1 to about 25.Preferred alkoxy silicones include certain commercially availableproducts such as, for example, alkoxy silicone SR 191 (trademark;General Electric Company, Waterford, N.Y.) which is a 100% siliconeresin having siloxane content of 88.9%, methoxy content of 15%, andnumber average molecular weight of 600. Another suitable alkoxy siliconeis SR-193 (trademark; General Electric Company), which is similar toSR-191, but contains certain silicone modifying agents and produces asomewhat more brittle product. Also suitable is Silikophen P50/300(trademark; available from Goldschmidt Chemical Corp., Hopewell, Va.) aphenyl methyl polysiloxane resin in a xylene/2-methoxypropanol-1solvent. Also suitable is Wacker Silicone-Intermediate SY- 231(trademark; Wacker-Chemie GmbH, Munich, Germany) which is taught for usein preparing polyesters and coating compositions and has an averagemolecular weight of 800, methoxy content of 14 weight percent, totalsilicone content of 89 weight percent (all methoxy groups replaced bySi--O--Si bonds) and SiO₂ content of 44 weight percent gravimetric.Mixtures of alkoxy silcones also may be used in reaction with the polyolreactant to prepare the hydroxy functional polysiloxane reactant.

Numerous suitable polyols for making the hydroxy functional polysiloxanereactant are known to the skilled of the art and will be readilyapparent in view of the present disclosure. Included are manycommercially available polyols and others which are readily preparedaccording to known methods. Preferably, the polyol comprises diol andtriol in hydroxyl equivalent ratio of from about 4:1 to about 1:4, morepreferably from about 3:1 to about 3:2.5, respectively. Suitable diolsinclude, but are not limited to, alkylene glycols, such as butyleneglycol, neopentyl glycol, 1,5-pentene glycol,3-cyclohexene-1,1-dimethylol, and other glycols such as hydrogenatedbisphenol A, caprolactone diol (e.g., the reaction product ofcaprolactone and ethylene glycol), hydroxy alkylated bisphenol,polyether glycols, e.g., poly(oxytetramethylene) glycol, polyesterdiols, e.g.,2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, and thelike. Preferred diols are neopentyl glycol and2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, thelatter material being commercially available as Esterdiol 204(trademark; Union Carbide Corp., Danbury, Conn.)

The polyol generally should comprise at least about 5 weight percenttriol and may consist substantially entirely of triol. The polyolcomponent also may comprise tetrols and higher functionality polyols,but these generally are less preferred. By employing diols in the polyolcomponent in addition to the triols, the flexibility of the coatingcomposition is generally increased. Thus, selection of the polyolcomponent to be used in forming the polysiloxane will be dependent onthe particular desired properties and application of the coatingcomposition. When diols are employed in the polyol component, the polyolpreferably comprises from about 10 to about 80 weight percent triols andfrom about 90 to about 20 weight percent diols. Preferred triols areconventional low molecular triols such as 1,2,6hexanetriol,1,1,1-trimethylolpropane, 3-(2-hydroxypropoxy)-1,2-propanediol andpolycaprolactone triols, which are commercially availabe as, forexample, Tone-301 (trademark; Union Carbide Corp., Danbury, Conn.).Additional preferred polycaprolatone triols are described in U.S. Pat.No. 4,165,345, incorporated herein by reference. Suitable tetrols willbe apparent also and include, for example, pentaerythritol and the like.

While a number of types of polyols have been mentioned above as suitablefor use in making the hydroxy functional polysiloxane reactant, theirdisclosure is not meant to be limiting. A great many additional suitablediols, triols, etc. are known in the art and selection of other polyolswhich would be suitable for use would be well within the skill of thosein the art in view of this disclosure.

The polyol reactant (i.e., diols, triols and optionally tetrols, etc.)and the second reactant (i.e., alkoxy silicone and, optionally,dicarboxylic acid or anhydride thereof) are combined and reacted,generally in the presence of a catalyst and at elevated temperatures, toproduce the aforesaid hydroxy functional polysiloxane. Suitablecatalysts for the carboxy/hydroxy condensation reaction include suchcatalysts as tetraisopropyl titanate, strong acids such as p-toluenephosphonic acid, phosphoric acid, sulfuric acid and materials such aszinc oxide, antimony oxide (Sb₂ O₃), dibutyl tin oxide, hydratedmonobutyl tin oxide, and sodium acetate. Other catalysts will beapparent to those skilled in the art in view of this disclosure. Thepolyol and second reactant are reacted preferably in such proportions asto provide a molar equivalent ratio of polyol OH to combined alkoxysilicone --OQ' (as defined above) and diacid COOH from about 6:2 toabout 6:5, respectively. Sufficient polyol must be used to provide ahydroxy functional product.

As noted above, the hydroxy functional polysiloxane is optionallyurethane modified and typically may contain about 1-10 urethane groupsper molecule. According to one embodiment of the invention, urethanegroups are introduced by reaction of the above-described hydroxyfunctional polysiloxane with organic diisocyanate. Such reaction iscarried out according to known methods, generally in the presence ofsolvents commonly employed for coating formulations such as toluene,xylene, methyl amyl ketone, and the like. Numerous suitable organicdiisocyanates are readily commercially available and will be apparent tothe skilled of the art in view of the present disclosure. Suitablediisocyanates include hydrocarbon diisocyanate or substitutedhydrocarbon diisocyanate, such as 1,6-hexamethylene diisocyanate,isophorone diisocyanate, p-phenylene diisocyanate, biphenyldiisocyanate, toluene diisocyanate, and 3,3-dimethyl-4,4-biphenylenediisocyanate. While the diisocyanate may be any of a number ofaliphatic, cycloaliphatic, and aromatic diisocyanates, it is preferredthat the diisocyanate be an aliphatic diisocyanate, such as4,4-dicyclohexylmethanediisocyanate. As would be apparent to thoseskilled in the art, mixtures of various diisocyanates may also beemployed as the diisocyanate component used in forming urethane-modifiedpolysiloxane. Typically, the hydroxy functional polysiloxane anddiisocyanate are reacted in such proportions as to provide about 4-10hydroxyl groups per isocyanate group.

While urethane modification may be introduced in the manner discussedabove, according to an alternative embodiment of the invention thepolyol reactant employed in reaction with the second reactant comprisesurethane modifiied polyol. In this case, there is no need to react withdiisocyanate the hydroxy functional polysiloxane. Employing urethanemodified polyol is found to provide a final resin, i.e., graftcopolymer, which is somewhat more flexible than when the urethane groupsare introduced by reaction of the hydroxy functional polysiloxane withdiisocyanate. Suitable urethane modified polyols are commerciallyavailable or readily prepared according to known methods. Exemplaryurethane modified diols are made by reaction of diol and diisocyanate ina molar ratio of from about 4:1 to about 4:3, preferably from about2:0.8 to about 2:1.2, more preferably about 2:1. Suitable diols anddiisocyanates include those mentioned above. Such ratio of diol todiisocyanate (i.e., a molar excess of diol) causes the reaction productto be substantially free of unreacted isocyanate groups. This urethanemodified diol is then combined with other portions of the polyolreactant (e.g., additional diol, triol, tetrol, etc.) for reaction withthe second reactant, generally at elevated temperature and in thepresence of a catalyst (as discussed above) to produce the hydroxyfunctional polysiloxane, specifically, a hydroxy functional urethanemodified polysiloxane. It will be apparent to those skilled in the art,that urethane modified triol, urethane modified tetrols, etc. can beused in addition to or in lieu of urethane modified diol, according tothe methods and guidelines discussed above, to provide hydroxyfunctional urethane modified polysiloxane.

Coating Compositions

According to another aspect of the invention, the above-describedhydroxy functional polysiloxane graft copolymer is employed in anorganic solvent based thermosetting coating composition together withsuitable polyfunctional hydroxy-reactive crosslinking agent. Suchcrosslinking agent is selected, preferably, from aminoplast crosslinkingagents and polyisocyanate crosslinking agents, either blocked orunblocked depending upon the intended application. Coating compositionsof the invention can be formulated so as to be suitable for numerousdifferent applications including, particularly, as motor vehicle bodypanel coatings. Thus, for example, a coating composition of theinvention can be formulated as a primer or as a topcoat, such as abasecoat fro a basecoat/clearcoat system, a clearcoat for abasecoat/clearcoat system, or as a one-coating topcoat. Moreover, any ofthese coatings can be formulated as either a one-component (i.e., resinand crosslinker combined) or a two-component (i.e., resin andcrosslinker segregated) coating composition, except that the basecoat ofa base/clear system generally would be formulated only as aone-component coating in view of the high pigment content thereof andthe mixing and dispersion problems which would result in attempting toadd the crosslinking agent at the time of application to a substrate. Itis, of course, well known to the skilled of the art to employ unblockedpolyisocyanate crosslinking agents generally only in two-componentformulations to prevent premature reaction thereof with the hydroxyfunctional copolymer. Blocked polyisocyanate crosslinkers are employedin one-component coatings, but typically these are employed in primerssince the two-component unblocked polyisocyanate coatings of theinvention are found generally to provide better surface appearance. Theamino resin crosslinking agents also are employed, typically, in onecomponent formulations.

In a coating composition intended for use as a high solids base coat orclear coat of a base/clear automotive coating formulation, typically itis preferred that the graft copolymer have a number average molecularweight (M_(n)) between about 1,500 and about 3,000, more preferablybetween about 1,500 and about 2,500. Also, for such use the resinpreferably has a hydroxy number between about 50 and about 150.

Crosslinking Agent

The crosslinking agent is generally included in compositions of theinvention in an amount between about 5 and about 60 weight percent,preferably in an amount between about 20 and about 50 weight percentbased on the weight of the copolymer and crosslinker combined. Selectionof the optimal amount of crosslinking agent to be employed in thecoating composition is dependent on the desired properties (e.g.,flexibility) of the coating as well as its intended use, and selectionof such amount would be within the skill of one in the art.

Polyisocyanate crosslinking agents are well known in the art andnumerous suitable organic isocyanates having 2 or more reactiveisocyanate groups per molecule will be apparent to those skilled in theart. Among the many suitable polyisocyanates are aliphatic,cycloaliphatic and aromatic isocyanate compounds. Representative of thenumerous isocyanates which can be employed are (1) aliphaticdiisocyanates such as trimethylene diisocyanate, tetramethylenediisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate,1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylenediisocyanate, 1,3-butylene diisocyanate, ethylidene diisocyanate,butylidene diisocyanate, 4,4'-bis(isocyanate hexyl)methane,bis(2-isocyanate-ethyl)fumarate, 2,6-diisocyanate methyl caproate,2,2,4-(2,4,4)-trimethylhexamethylene diisocyanate, and dimer aciddiisocyanates; (2) cycloaliphatic diisocyanates such as 1,3-cyclopentanediisocyanate, 1,4-cyclopentane diisocyanate, 1,2-cyclopentanediisocyanate, and methylcyclohexylene diisocyanate; (3) aromaticdiisocyanates such as m-phenylene diisocyanate, p-phenylenediisocyanate,4,4'-diphenyl diisocyanate; (4) aliphatic/aromatic diisocyanates such as4,4'-diphenylene methane diisocyanates, 2,4- or 2,6-tolylenediisocyanate, 4,4'-toluidene diisocyanate, 1,4-xylylene diisocyanate;(5) nuclear substituted aromatic compounds such as dianisidinediisocyanate, 4,4'-diphenylether diisocyanate, chlorodiphenylenediisocyanate; (6) triisocyanates such astriphenylmethane-4,4',4"-triisocyanate, 1,3,5-triisocyanate benzene,2,4,6-triisocyanate toluene; (7) tetraisocyanates such as 4,4'-diphenyldimethylmethane 2,2',5,5'-tetraisocyanate; (8) polymerized isocyanatessuch as tolylene diisocyanate dimers and trimers and the like; and (9)polyisocyanates such as prepolymers derived from a polyol, includingpolyether polyols or polyester polyols (including polyethers which arereacted with excess polyisocyanates to form isocyanate terminatedprepolymers), simple polyols such as glycols (e.g., ethylene glycol,propylene glycol), other polyols such as glycerol, trimethylol propane,hexane triols, pentaerythritol and the like, as well as monoethers,e.g., diethylene glycol, tripropylene glycol and the like, andpolyethers, i.e., alkylene oxide condensates of the above. While thepolyisocyanate crosslinking agent may be any organic polyisocyanate ashas been noted above, such crosslinking agents for coating compositionto be employed as clear (top) coats are preferably aliphatic andcycloaliphatic polyisocyanates, due to their superior weatherability.

Especially preferred for use in clearcoat compositions of the inventionare trimerized products of aliphatic diisocyanates such as1,6-hexamethylene diisocyanate. Still another particularly preferredtype of crosslinking agent is a polyisocyanate having a biuretstructure. This type of polyisocyanate is well known, as are methods formaking the same. Suitable such polyisocyanate crosslinking agents arehigh molecular weight biurets of 1,6-hexamethylene diisocyanate sold byMobay Chemical Company under the trademarks Desmodur N and DesmodureL-2291. Exemplary of other biuret type polyisocyanates are thoseprepared in accordance with U.S. Pat. No. 3,976,622 to Wagner et al.

Blocked polyisocyanate crosslinking agents are well known to the skilledof the art and many suitable for use in compositions of the inventionare commercially available or readily prepared and will be apparent fromthe present disclosure. More specifically, blocked polyisocyanatecrosslinking agents comprise the reaction product of a polyisocyanate,such as those mentioned above, with a blocking agent, that is, an activehydrogen-bearing reactant. Exemplary blocked polyisocyanates aredescribed, for example, in U.S. Pat. No. 4,497,938, which description isincorporated herein by reference. Blocked polyisocyanate crosslinkingagents are used generally in the same proportions disclosed above forunblocked polyisocyanate crosslinking agents.

Amine-aldehyde crosslinking agents suitable for crosslinking hydroxyfunctional bearing materials are well known in the art. Typically, thesecrosslinking materials are products of reactions of melamine, or ureawith formaldehyde and various alcohols containing up to and including 4carbon atoms. Preferably, the amine-aldehyde crosslinking agents areamine-aldehyde resins such as condensation products of formaldehyde withmelamine, substituted melamine, urea, benzoguanamine or substitutedbenzoguanamine. Preferred members of this class are methylatedmelamine-formaldehyde resins such as hexamethoxymethylmelamine.Particularly preferred crosslinkers are the high solids melamine resinswhich have substantially 95+ percent nonvolatile content. For so-called"high solids" compositions of this invention, it should be recognizedthat it is important not to introduce extraneous diluents that lower thefinal solids content of the coating. Other suitable amine-aldehydecrosslinking agents will be apparent to one skilled in the art.Amine-aldehyde crosslinking agents are preferred for basecoatcompositions of the invention. The amine-aldehyde crosslinking agent isgenerally included in a basecoat composition in an amount of betweenabout 5 and about 60, preferably between about 20 and about 40 weightpercent. However, selection of the particular amount of amine-aldehydecrosslinking agent to be employed in any such composition is dependenton the desired properties of the composition as well as its intended useand would be apparent to one skilled in the art.

Particular preferred crosslinking agents are the amino crosslinkingagents sold by American Cyanamid under the trademark "Cymel". Inparticular, Cymel 301, 303, 325, 1130, 1156, 1161 and 1168 (trademarks)are alkalated melamine aldehyde resins useful in the compositions ofthis invention. The crosslinking reactions are catalytically acceleratedby acids. One such catalyst, for example, which may be so employed isp-toluene sulfonic acid, which when employed is generally added to thecomposition in about 0.5% by weight based on the total weight of thegraft copolymer and crosslinking agent.

Additional Materials

Additional materials which may be employed in the coating compositionsof this invention include a high molecular weight linear polyurethanewhich has a number average molecular weight of between about 15,000 andabout 40,000, preferably between about 20,000 and about 30,000. It maybe made by reacting one of the above mentioned diisocyanates and diols,such as oligoester diol, polycaprolactone diol, polyoxypropylene diol,polyether diols, etc. Suitable high molecular weight linear polyurethanematerials are commercially available, for example, as Spenlite LO6-30S,(trademark, Spencer-Kellogg, Buffalo, N.Y.). It has been found thatthese high molecular weight polyurethanes may be employed in metallicflake pigment-bearing topcoat compositions in small amounts, typicallyup to about 15 weight percent based on the total weight of the polyestergraft copolymer and crosslinking agent, to improve the orientation ofthe metallic flake pigment in the cured coating. It has been found thatby including such linear polyurethane, for example, in a basecoat of abasecoat/clearcoat system, the depth of color and metallic glamour ofthe system may be improved.

Other materials which may be included in the coating compositions ofthis invention include, for example, catalysts, antioxidants, U.V.absorbers (for topcoats), solvents, surface modifiers and whiteningagents. Solvents used in the coating composition of this invention arethose which are commonly used, e.g., to facilitate spray application andhigh solids content and include toluene, xylene, methylethyl ketone,acetone, 2-ethoxy-1-ethanol, diacetone alcohol, tetrahydrofuran, ethylacetate, dimethylsuccinate, dimethylglutarate, dimethyladipate andmixtures thereof. The solvent in which the polysiloxane graft copolymeris prepared may be employed as a solvent for the composition, thuseliminating the need for drying the resin after preparation, if such isdesired.

Typical ultraviolet light stabilizers that are useful in topcoatcompositions of this invention are benzophenones such as dodecyloxibenzophenone, 2,4-dihydroxybenzophenone, hydroxybenzophenonescontaining sulfonic groups,2,4-dihydroxy-3',5'-ditertiarybutylbenzophenone,2,2',4'-trihydroxybenzopheone esters of dicarboxylic acids,2-hydroxy-4-acryloxyethoxybenzophenone, aliphatic monoesters of2,2',4-trihydroxy-4'-alkoxybenzophenone,2-hydroxy-4-methoxy-2-carboxybenzophenone, triazoles such as2-phenyl-4-(2'4'-dihydroxybenzolyl)-triazoles, substitutedbenzotriazoles such as hydroxyphenyltriazoles such as2-(2'-hydroxy-5'-methylphenyl)benzotriazole,2-(2'-hydroxyphenyl)benzotriazole, and2-(2'-hydroxy-5'-octylphenyl)naphthiotriazole.

Another type of ultraviolet light stabilizer and one that isparticularly preferred for use in the coatings of this invention is thattaught in U.S. Pat. No. 4,480,084 entitled "Polymeric Light Stabilizers"to Kordomenos et al. These stabilizers contain the sterically hinderedpolyalkylpiperidine radical and at least two primary hydroxyl groupsavailable for reacting with the crosslinking agent, e.g., amine-aldehydeor polyisocyanate, of the coating composition.

Typical antioxidants which may be employed in the coating compositioninclude tetrakis alkylene (di-alkyl hydroxy aryl) alkyl ester alkanessuch as tetrakis methylene3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)proprionate methane (availableunder the trademark Irganox 1010 from Ciba-Geigy Corp.). Also suitableare the reaction product of p-amino diphenylamine and glycidylmethacrylate, the reaction product of n-hexyl-N'-phenyl-p-phenylenediamine and glycidyl methacrylate, pentaerythritoltetrakis(thioglycolate), trimethylol propane tris(thioglycolate),trimethylol ethane tris(thioglycoate), N-(4-anilinophenyl)maleimide,alkylhydroxyphenyl groups bonded through carboalkoxy linkages tonitrogen atom of a heterocyclic nucleus containing an imidodicarbonylgroup or an imidodithiocarbonyl group,3,3-ditertbutyl-4-hydroxy-cinnamonitrile,ethyl-3,5-diterthexyl-4-hydroxy-cinnamate, substituted benzyl esters ofbeta-substituted (hydroxyphenyl)-propionic acids,bis-(hydroxyphenylalkylene)alkyl isocyanurate compounds, tetrakishydroxy benzyl phosphonium halides alone or in combination with adialkylthiodialkanoate, thiodimethylidyne tetrakisphenols alone or incombination with a dialkyl thiodialkanoate or phosphite or phosphonate,dihydrocarbyl-hydroxyphenyl aryl or alkyl phosphonites or phosphonatesor phosphates or phosphinites or phosphinates or phosphionites orphosphorothionates or phosphinothionates,diphenyl-bis(3,5-ditertbutyl-4-hydroxyphenoxy)silane,hydrocarbylhydroxyphenyl-dihydrocarbyldithio-carbamates such as3,5-ditertbutyl-4-hydroxyphenyl dimethyldithiocarbamate and amino benzylthioether.

In one preferred embodiment a base/clear topcoat system is provided,wherein both the basecoat and the clearcoat comprise a resin andcrosslinker composition according to the invention. The basecoat wouldpreferably contain only a benzotriazole U.V. stabilizer such as Tinuvin328 (trademark, Ciba-Geigy, Ardsley, N.Y.), and the clearcoat wouldcontain a benzotriazole U.V. stabilizer, e.g., Tinuvin 328, thepolymeric hindered amine light stabilizer of the aforementioned U.S.Pat. No. 4,480,084 to Kordomenos et al and an antioxidant, e.g.,Irganox-1010 (trademark; Ciba-Geigy). While preferred combinations ofstabilizers and antioxidants have been described, these teachings arenot meant to be limiting. Selection of suitable stabilizers andantioxidants is within the skill of one in the art.

Surface modifiers or wetting agents are common additives for liquidpaint compositions. The exact mode of operation of these surfacemodifiers is not known, but it is thought that their presencecontributes to better adhesion of coating compositions to the surfacebeing coated and helps formation of thin coatings, particularly on metalsurfaces. The choice of surface modifiers or wetting agents is dependentupon the type(s) of surface to be coated. Selection of appropriatesurface modifiers is well within the skill of the art. Typical of thesesurface modifiers are polybutyl acrylate and a wide variety of siliconwetting agents which are commercially available.

For many applications of the coating compositions of the invention,particularly high solids compositions, it may be desirable to employflow control additives to provide sag free coatings. Among the many suchmaterials which are known are non-aqueous dispersions (NAD's) such asdescribed by Porter (S. Porter, Jr., and B. N. McBane, U.S. Pat. No.4,025,474, May 24, 1977). These particle dispersions may be includedgenerally in an amount up to 15% by weight of the total composition.Other types of NAD's such as described by D. L. Maker and S. C. Peng(U.S. Pat. No. 3,814,721, June 4, 1974) or by S. K. Horvath (U.S.application Ser. No. 292,853, filed Aug. 14, 1981, now U.S. Pat. No.4,415,681) also may be included in the coating compositions.

Coating compositions according to certain embodiments of the inventionmay contain pigments. Thus, for example, primer compositions and thebasecoat of a base/clear system may comprise any of the wide variety ofsuitable pigments which are known to the art and readily commerciallyavailable. Selection of suitable pigments and the amounts of same willdepend largely on the intended use and desired properties of thecoating, for example, desired color, hiding properties, etc., and iswithin the skill of those in the art.

The coating composition can be applied by conventional methods known tothose in the art. These methods include roll coating, spray coating,dipping or brushing. The particular application technique chosen willdepend upon the particular substrate to be coated and the environment inwhich the coating operation takes place. Preferred techniques forapplying these coating compositions, particularly when applying the sameto automobiles, is spray coating through the nozzle of the spray gun. Abasecoat, for example, can be applied as a single component by means ofa single component spray gun. On the other hand, in spray applying a twocomponent clearcoat composition, the polysiloxane graft copolymer andadditives such as pigments, U.V. absorbers, antioxidants and othernonreactive materials are admixed with a solvent. These materials arefed as one component of a two component system into a spray gun whichcombines the materials as they are sprayed into the automotivesubstrate. The other material is the polyisocyanate crosslinking agent,which may or may not be cut with a suitable nonreactive solvent.

The invention will be further understood by referring to the followingdetailed examples. It should be understood that the specific examplesare presented by way of illustration and not by way of limitation.Unless otherwise specified, all references to "parts" are intended tomean parts by weight.

EXAMPLE I

Hydroxy functional oligomeric polysiloxane reactant was preparedaccording to this example. In a suitable reactor 1836 g Esterdiol-204(trademark; Union Carbide, Danbury, Conn.;2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate), 552 gtrimethylolpropane, 1314 g adipic acid, and 190 g SR-191 (trademark;General Electric Co.; methoxy functional silicone resin) were charged.The mixture was heated to 300° F. and a mixture of water and methanolwas distilled off until the acid number dropped below 10. The batch wasthen thinned with 1535 g xylene. The final product had a viscosity of Kat 70% non-volatiles.

EXAMPLE II

Hydroxy functional oligomeric polysiloxane reactant was preparedaccording to this example. In a suitable reactor 300 g triethyleneglycol, 300 g SR-191 (trademark; General Electric) and 1.1 g Ken-KemTIPT (trademark; Kenrich Petrochemical, Inc.; titanium catalyst) werecharged. The mixture was heated at 300° F. until 85% of the totaltheoretical methanol was evolved. At this point the batch was thinnedwith 200 g Solvesso 100 to yield a resin with an A viscosity at 72%non-volatiles.

EXAMPLE III

Hydroxy functional oligomeric polysiloxane reactant was preparedaccording to this example. In a suitable reactor 400 g Solvesso 100, 300g triethylene glycol, and 2.2 g Ken-Kem TIPT (trademark; KenrichPetrochemical, Inc.; titanium catalyst) were charged. The mixture washeated to 250° F. at which time 194 g alkoxy silicone SR-193 (trademark;General Electric Co.) was added dropwise. After addition was complete,the mixture was heated at 250° F. until approximately 50% of thetheoretical methanol was evolved. The reaction mixture was cooled to200° F. and 146 g adipic acid and 88 g trimethylol propane were charged.The mixture was heated at 300° F. and water was distilled off until theacid number dropped below 10. The final product had a viscosity of A at55% non-volatiles and an acid number of 9.

EXAMPLE IV

Hydroxy functional oligomeric polysiloxane reactant was preparedaccording to this example. In a suitable reactor 1530 g Esterdiol 204(trademark; Union Carbide Corp.; diol), 1095 g adipic acid, 660 gtrimethylolpropane, and 3 g Fascat 4100 (trademark; M&T Chemicals, Inc.;catalyst) were charged. The mixture was heated at 300°-340° F. and waterdistilled off until the acid number dropped below 10. At this point thebatch was thinned with 1300 g xylene to yield a resin with a viscosityof R at 70% non-volatiles and an acid number of 4. Subsequently, suchproduct resin (1000 g) was charged into a suitable reactor together with49 g alkoxy silicone SR-191 (trademark; General Electric Co.), and 3.5 gbenzoic acid. The mixture was heated at 225° F. until 75% of the totaltheoretical methanol was evolved. The resulting resin had a viscosity ofL at 68% non-volatiles.

EXAMPLE V

Hydroxy functional polysiloxane reactant was prepared according to thisexample. In a suitable reactor 425 g of the resin from Example II, 73 gadipic acid, and 44 g trimethylol propane were charged. The mixture washeated at 300° F. and water was distilled off until the acid numberdropped below 5. The final product had a viscosity of D-E at 77%non-volatiles.

EXAMPLE VI

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer was prepared according to this example. In asuitable reactor 1085 g of the resin from Example I, 911 g xylene, and4.13 g Shell 1201 (trademark; Shell Chemical Co.) catalyst were charged.The mixture was heated to 200° F. and 53.6 g glycidyl methacrylate wasadded dropwise at such rate that addition was complete in 20 minutes. Atthis point 83 mg hydroquinone was added and the mixture was furtherheated at 200° F. until the weight per epoxy (WEP) of the product resinwas above 2000. The final resin had a viscosity less than A at 36%non-volatiles.

EXAMPLE VII

Hydroxy functional polysiloxane reactant was prepared according to thisexample. In a suitable reactor 400 g of the resin from Example II, 40 gtrimethylol propane, 131 g adipic acid, and 0.6 g Fascat 4100(trademark; M and T Chemicals, Inc.; catalyst) were charged. The mixturewas heated at 300° F. and water was distilled off until the acid numberdropped below 10. The resulting resin had a W viscosity at 92%non-volatiles.

EXAMPLE VIII

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer was prepared according to this example. In asuitable reactor 800 g of the resin from Example III, 0.4 g Shell 1201(trademark; Shell Chemical Co.) catalyst, 50 mg hydroquinone, and 800 gxylene were charged. The mixture was heated at 200° F. and 34 g glycidylmethacrylate were added dropwise over a period of 10 minutes. Afteraddition was complete, the mixture was further heated at 200° F. untilthe WPE was greater than 2000. The resulting resin had an A viscosity at53% non-volatiles.

EXAMPLE IX

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer was prepared according to this example. In asuitable reactor 500 g of the resin of Example V, 0.31 g Shell 1201(trademark; Shell Chemical Co.) catalyst, 40 mg hydroquinone, and 630 gxylene were charged. This mixture was heated to 200° F. at which time 27g glycidyl methacrylate was added dropwise at such a rate that additionwas complete in 40 minutes. The mixture was further heated at 200° F.until the WPE rose above 2000. The resulting resin had an A viscosity at31% non-volatiles.

EXAMPLE X

Hydroxy function polysiloxane graft copolymer was prepared according tothis example. In a suitable reactor 440 g xylene and 7.2 g cumenehydroperoxide were charged. This mixture was heated to 280° F. and amixture of 1784 g of the resin from Example VI, 242 g butylmethacrylate, 24 g hydroxyethyl acrylate, 50 g styrene, 12 g acrylicacid, and 7.2 g t-butylperbenzoate was added dropwise over a period offive hours. The mixture was postreacted at 280° F. for two hours. Thetemperature was raised to 300° F. and 880 g of xylene were stripped off.The final product had a viscosity of F at 62% non-volatiles.

EXAMPLE XI

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer was prepared according to this example. In asuitable reactor 400 g of the resin from Example VII, 0.3 g Shell 1201(trademark; Shell Chemical Co.) catalyst, 40 mg hydroquinone and 599 gxylene were charged. The mixture was heated to 200° F. at which time 26g glycidyl methacrylate was added dropwise over a period of one hour.The mixture was further heated at 200° F. until the WPE rose above 2000.The resulting resin had a viscosity of A at 47% non-volatiles.

EXAMPLE XII

Hydroxy functional polysiloxane graft copolymer was prepared accordingto this example. In a suitable reactor 375 g xylene and 5.6 g cumenehydroperoxide were charged. The temperature was raised to 270° F. and amixture of 1500 g of the resin from Example VIII, 207 g butylmethacrylate, 20 g hydroxypropyl methacrylate, 43 g styrene, and 5.6 gt-butylperbenzoate was added dropwise over a period of five hours. Themixture was postreacted at 275° F. for two hours. The temperature wasraised to 300° F. and 1080 g of xylene were stripped off. The finalproduct had a viscosity of F at 67% non-volatiles.

EXAMPLE XIII

Hydroxy functional polysiloxane graft copolymer was prepared accordingto this example. In a suitable reactor 218 g of xylene and 3.6 g cumenehydroperoxide were charged. The mixture was heated to 270° F. at whichtime a mixture of 900 g of the resin from Example IX, 120 g butylmethacrylate ("BMA"), 12 g hydroxypropyl methacrylate ("HPMA"), 25 gstyrene, and 3.6 g t-butylperbenzoate were added. The mixture waspostreacted at 270° F. for two hours. The temperature was raised to 300°F. and 544 g xylene were stripped off. The final product had a Kviscosity at 64% non-volatiles.

EXAMPLE XIV

Hydroxy functional polysiloxane graft copolymer was prepared accordingto this example. In a suitable reactor 330 g of xylene and 5 g cumenehydroperoxide were charged. The mixture was heated to 270° F. and amixture of 900 g of the resin from Example XI, 128 g butyl methacrylate,18 g hydroxypropylmethacrylate, 38 g styrene, and 5 g t-butylperbenzoatewas added over a period of five hours. The mixture was postreacted fortwo hours at 270° F. The temperature was raised to 300° F. and 680 g ofxylene were stripped off. The final product had a viscosity of R at 70%non-volatiles.

EXAMPLES XV-XXI

One and two component flexible clear coat compositions ("flexible"referring to the cured coating) suitable for use in a base/clearautomotive coating system were formulated according to the compositionsin Table A. The order of addition was as follows. In the case of onecomponent coatings formulated with Cymel 1130 (trademark; AmericanCyanamid Co.: alkylated melamine crosslinking agent), the resin wasmixed with n-butylacetate, a UV-stabilizer/absorber package (a solutionof 25 parts TIN 079L, 8 parts TIN 900, 7 parts TIN 328 (trademarks;Ciba-Geigy Co.) and 60 parts xylene), butyl acrylate, methyl amylketone, and Tetralin. This mixture was added to a premixed solution ofCymel 1130, acid catalyst (para-toluene sulfonic acid, 40% solution inbutanol), cellosolve acetate, and xylene. The viscosity of the coatingformulation was adjusted to 20 sec #4 Ford Cup (80° F.) with a mixtureof 8:2 (W/W) xylene and 2-ethyl hexanol. In the case of two componentcoatings formulated with an organic polyisocyanate, the resin was mixedwith n-butyl acetate, a UV stabilizer/absorber package (same as above),butyl acrylate, methyl amyl ketone, and Tetralin. To this mixture thepolyisocyanate, predissolved in xylene and cellosolve acetate, was addedjust before spraying. The viscosity of the coating formulation wasadjusted to 20 sec # 4 Ford Cup (80° F.) with xylene. Bonderite steelpanels and RIM panels were sprayed first with a high solids basecoat andthe clearcoat was applied wet on wet. The panels were baked at 250° F.for 30 minutes to give smooth, tough films with excellent flexibilityand excellent chemical and oxidative resistance.

                                      TABLE A                                     __________________________________________________________________________    CLEARCOAT COMPOSITIONS                                                                        EXAMPLE                                                       COMPOSITION     XV XVI                                                                              XVII                                                                              XVIII                                                                             XIX                                                                              XX XXI                                       __________________________________________________________________________    Resin of Example X                                                                            68.7          68.7                                            Resin of Example XII                                                                             63.6          63.6                                         Resin of Example XIII 66.6                                                    Resin of Example XIV      60.9      60.9                                      n-butyl acetate 7.2                                                                              7.2                                                                              7.2 7.2 7.2                                                                              7.2                                                                              7.2                                       UV stabilizer/absorber package                                                                13.8                                                                             13.8                                                                             13.8                                                                              13.8                                                                              13.8                                                                             13.8                                                                             13.8                                      polybutyl acrylate                                                                            0.96                                                                             0.96                                                                             0.96                                                                              0.96                                                                              0.96                                                                             0.96                                                                             0.96                                      methyl amyl ketone                                                                            18.2                                                                             18.2                                                                             18.2                                                                              18.2                                                                              18.2                                                                             18.2                                                                             18.2                                      Tetralin.sup.1  12 12 12  12  12 12 12                                        xylene          10 10 10  10  14 14 14                                        cellosolve acetate                                                                            1  1  1   1   1  1  1                                         acid catalyst 1.2                                                                             1.2                                                                              1.2                                                                              1.2                                                     Cymel 1130.sup.2                                                                              14.1                                                                             14.1                                                                             14.1                                                                              14.1                                                Desmodur N-3390.sup.3         22.82                                                                            22.8                                                                             22.8                                      __________________________________________________________________________     .sup.1 1,2,3,4tetrahydronaphthalene.                                          .sup.2 Trademark; American Cyanamid Company; alkylated melamine               crosslinking agent.                                                           .sup.3 Trademark; Mobay Chemical Corporation; polyisocyanate crosslinking     agent.                                                                   

EXAMPLES XXII-XXIV

One component, high solids, flexible base coat compositions suitable foruse in a base/clear automotive coating system were formulated accordingto the compositions shown in Table B. The components were added in theorder listed and in the manner, generally, described for one componentclear coat compositions of the preceding examples. The compositions werereduced to 20 sec #4 Ford Cup (80° F.) with methyl amyl ketone beforespraying.

                  TABLE B                                                         ______________________________________                                        BASECOAT COMPOSITIONS                                                                       EXAMPLE                                                         COMPOSITION     XXII       XXIII   XXIV                                       ______________________________________                                        Resin of Example X                                                                            125                                                           Resin of Example XIII      125                                                Resin of Example XIV               110                                        Spenlite LO6-305.sup.1                                                                        19.2       19.2    19.2                                       Cymel 1130.sup.2                                                                              52.4       52.4    52.4                                       Cymel 1161.sup.2                                                                              35.2       35.2    35.2                                       Tinuvin-328.sup.3                                                                             9.6        9.6     9.6                                        para-toluene sulfonic                                                                         2.0        2.0     2.0                                        acid solution (40%                                                            in butanol)                                                                   5000-AR.sup.4   123        123     123                                        Microgel flow control                                                                         96         96      96                                         additive.sup.5                                                                Esterdiol-204.sup.6                                                                           46         46      46                                         cellosolve acetate                                                                            19.2       19.2    19.2                                       aluminum stearate                                                                             96         96      96                                         xylene          15.4       15.4    15.4                                       isopropyl alcohol                                                                             15.4.      15.4    15.4                                       ______________________________________                                         .sup.1 Trademark; SpencerKellog, Buffalo, N.Y.; linear polyurethane           modifying agent for aluminum pigment orientation.                             .sup.2 Trademark; American Cyanamid Co., Wayne, N.J.; alkylated melamine      crosslinking agent.                                                           .sup.3 Trademark; CibaGeigy; U.V. absorber.                                   .sup.4 Trademark; Silberline Co., Lansford, PA.; aluminum paste.              .sup.5 Prepared according to Examples 1-3 of U.S. Pat. No. 4,425,450.         .sup.6 Trademark; Union Carbide Corp.; diol.                             

EXAMPLE XXV

A millbase was prepared by grinding in a ball mill the followingmixture:

    ______________________________________                                        Composition        Parts                                                      ______________________________________                                        Resin of Example XIV                                                                             100                                                        Anti-Terra U       19                                                         Barium sulfate     547                                                        TiO.sub.2          103                                                        Carbon black       4                                                          Xylene             150                                                        Toluene            50                                                         ______________________________________                                    

A two component primer coating composition was formulated by mixing thefollowing components:

    ______________________________________                                        Composition        Parts                                                      ______________________________________                                        Millbase (above)   746                                                        Resin of Example XIV                                                                             425                                                        Desmodur L-2291A.sup.1                                                                           150                                                        Methyl amyl ketone 50                                                         ______________________________________                                         Trademark; Mobay Chemical Corp.; polyisocyanate crosslinking agent.      

The above composition was mixed quickly (within 5 minutes), reduced to19 sec #4 Ford Cup (80° F.) and sprayed over both Bonderite steel panelsand plastic panels. The panels were baked for 30 minutes at 250° F. togive smooth, tough films with excellent solvent resistance (20+ MEKrubs).

EXAMPLES XXVI-XXVII

Two component enamel coatings were formulated according to thecompositions shown in Table C. The order of addition was as follows:First the resin was mixed with the flow control additive, cellosolveacetate butyrate and 2-ethyl hexyl acetate. Subsequently, the aluminumpaste was predissolved in 15 parts of butyl cellosolve acetate and addedto the mixture. After the aluminum paste was dispersed, the rest of thebutyl cellosolve acetate was added. To this mixture the polyisocyanatecrosslinking agent, predissolved in 30 parts of methyl amylketone, wasadded just before spraying the coating. The viscosity of the paint wasadjusted to 20 sec #4 Ford Cup (80° F.) with methyl amyl ketone.Bonderite steel panels and plastic panels were sprayed and baked for 30minutes at 250° F. to give smooth, tough films with excellentflexibility and MEK resistance.

                  TABLE C                                                         ______________________________________                                        Composition          XXVI    XXVII                                            ______________________________________                                        Resin of Example XIV 197     197                                              Microgel flow control additive.sup.1                                                               5       5                                                Cellosolve acetate butyrate.sup.2                                                                  2       2                                                2-Ethyl hexyl acetate                                                                              15      15                                               Aluminum paste.sup.3 9       9                                                Butyl cellosolve acetate                                                                           50      50                                               Desmodur L-2291.sup.4                                                                              71                                                       Desmodur Z-4370.sup.4        107                                              Methyl amyl ketone   30      30                                               ______________________________________                                         .sup.1 Prepared according to Examples 1-3 of U.S. Pat. No. 4,425,450.         .sup.2 Eastman Chemical Co.; CAB 3810.1 (trademark).                          .sup.3 Silberline Co.,; 8199AR (trademark).                                   .sup.4 Trademark; Mobay Chemical Corp.; polyisocyanate crosslinking agent                                                                              

EXAMPLE XXVIII

Hydroxy functional polysiloxane reactant was prepared according to thisexample. In a suitable reactor were charged 1836 g Esterdiol 204(trademark; Union Carbide Corp.; diol), 552 g trimethylol propane, 1226adipic acid, and 360 g SR-191 (trademark; General Electric Co.; alkoxysilicone). The mixture was heated to 350° F. and a mixture of methanoland water was distilled off until the acid number dropped below 10. Thebatch was thinned with 1568 g xylene to afford a resin with a viscosityof D-E at 67% non-volatiles and an acid number of 6.3.

EXAMPLE XXIX

Hydroxy functional polysiloxane reactant was prepared according to thisexample. In a suitable reactor were charged 850 g Esterdiol 204(trademark; Union Carbide Corp.; diol), 276 g trimethylol propane, 657 gadipic acid, and 225 g SR-882 (trademark; General Electric Co.; alkoxysilicone). The mixture was heated to 300° F. and water distilled offuntil the acid number dropped below 10. The resin was thinned with 820 gxylene to afford a resin with a viscosity of F at 68% non-volatiles andan acid number of 8.5.

EXAMPLE XXX

Hydroxy functional polysiloxane reactant was prepared according to thisexample. In a suitable reactor 1836 g Esterdiol 204 (trademark; UnionCarbide Corp.; diol), 552 g trimethylol propane, 636 g adipic acid, 645g phthalic anhydride, and 360 g SR-191 (trademark; General Electric Co.;alkoxy silicone) were charged. The mixture was heated at 250° F. and amixture of water and methanol distilled off until the acid numberdropped below 10. The resin was thinned with 1600 g xylene to afford aresin with a viscosity of K at 72% non-volatiles.

EXAMPLE XXXI

The hydroxy functional polysiloxane reactant prepared according toExample I was urethane modified according to this example. In a suitablereactor was charged 1000 g of the resin from Example I. The resin washeated to reflux and any water present was distilled off. Thetemperature was lowered to 200° F. and 78 g Desmodur W (trademark; MobayChemical Co.; organic diisocyanate) was added dropwise over a period oftwo hours. The mixture was postreacted at 240° F. until no NCO group wasobserved in an IR spectra. The resulting hydroxy functional polysiloxanereactant had a viscosity of X-Y at 71% non-volatiles.

EXAMPLE XXXII

The hydroxy functional polysiloxane reactant prepared according toExample I was urethane modified according to this example. In a suitablereactor 1000 g of the resin from Example I was charged. The resin washeated to reflux and any water present was distilled off. Thetemperature was lowered to 250° F. and 124 g Desmodur W (trademark;Mobay Chemical Co.; organic diisocyanate) was added dropwise over aperiod of two hours. The mixture was postreacted at 240° F. until no NCOgroup was observed in an IR spectra. The resulting hydroxy functionalpolysiloxane reactant had a viscosity of Z₅ at 69% non-volatiles.

EXAMPLE XXXIII

The hydroxy functional polysiloxane reactant prepared according toExample XXVIII was urethane modified according to this example. In asuitable reactor 1500 g of the resin from Example XXVIII was charged.The resin was heated to reflux and any water present was distilled off.The temperature was lowered to 200° F. and 111 g Desmodur W (trademark;Mobay Chemical Co.; organic diisocyanate) was added dropwise over aperiod of two hours. The mixture was postreacted at 225° F. until no NCOgroup was observed in an IR spectra. The resulting hydroxy functionalpolysiloxane reactant had a viscosity of Z₁ -Z₂ at 79% non-volatiles.

EXAMPLE XXXIV

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer (urethane modified) was prepared according to thisexample. In a suitable reactor 850 g of the resin from Example XXXI, 0.5g Shell 1201 (trademark; Shell Chemical Co.) catalyst, 70 mghydroquinone, and 990 g xylene were added. The mixture was heated to200° F. and 45 g glycidyl methacrylate was added dropwise over a periodof 30 minutes. The mixture was postreacted at 200° F. until the WPE roseto a value greater than 2000. The final resin had a viscosity of A at32% non-volatiles and a WPE greater than 6000.

EXAMPLES XXXV

Hydroxy functional polysiloxane graft copolymer (urethane modified) wasprepared according to this example. In a suitable reactor 200 g xyleneand 3.6 g cumene hydroperoxide were charged. The mixture was heated to275° F. at which time a mixture of 892 g of the resin from ExampleXXXIV, 121 g butyl methacrylate, 12 g hydroxypropyl methacrylate, 25 gstyrene, and 3.6 g t-butylperbenzoate was added dropwise over 5 hours.The mixture was postreacted at 280° F. and 525 g of xylene distilledoff. The final resin had a K viscosity at 66% non-volatiles.

EXAMPLE XXXVI

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer (urethane modified) was prepared according to thisexample. In a suitable reactor 1000 g of the resin from Example XXXII,0.6 g Shell 1201 catalyst, 70 mg hydroquinone, and 113 g xylene wereadded. The mixture was heated to 200° F. and 49 g glycidyl methacrylatewas added over a 20 minute period. The mixture was postreacted at 200°F. until the WPE rose above 2000. The final resin had an A viscosity at31% non-volatiles.

EXAMPLE XXXVII

Hydroxy functional polysiloxane graft polymer (urethane modifiedy wasprepared according to this example. In a suitable reactor 240 g xyleneand 3.7 g cumene hydroperoxide were charged. The mixture was heated to270° F. at which time a mixture of 1000 g of the resin from ExampleXXXVI, 132 iso-butyl metacrylate, 13 g hydroxyethyl acrylate, 28 gstyrene, 3.7 t-butyl perbenzoate, and 15 g acrylic acid was addeddropwise over a period of 5 hours. The mixture was heated at 270° F. foran additional 2 hours. The mixture was brought to reflux and 690 gxylene stripped off to yield a final resin with a viscosity of Z₅ at 68%non-volatiles.

EXAMPLE XXXVIII

The hydroxy functional polysiloxane reactant of Example XXVIII wasurethane modified according to this example. In a suitable reactor 1500g of the resin from Example XXVIII was charged. The resin was heated to250° F. and 176 g Desmodur W (trademark; Mobay Chemical Co.;diisocyanate) was added dropwise over a period of 2 hours. The mixturewas postreacted at 230° F. until no NCO group was observed in an IRspectra. The resultant hydroxy functional polysiloxane reactant had aviscosity of Z₇ at 80% non-volatiles.

EXAMPLE XXXIX

Hydroxy functional carbon-carbon double bond-bearing branchedpolysiloxane macromer (urethane modified) was prepared according to thisexample. In a suitable reactor 400 g of the resin from Example XXXVIII,0.26 g Shell 1201 (trademark; Shell Chemical Co.) catalyst, 40 mghydroquinone, and 522 g xylene were charged. The mixture was heated to200° F. and 23 g glycidyl methacrylate was added dropwise over 40minutes. The mixture was postreacted at 200° F. until the WPE rose above2000. The final resin had a viscosity of A at 34% non-volatiles.

EXAMPLE XL

Hydroxy functional polysiloxane graft copolymer (urethane modified) wasprepared according to this example. In a suitable reactor 240 g Exxate600 (trademark; Exxon Chemical Co.,; oxyl hexyl acetate) and 3.6 gcumene hydroperoxide were charged. The mixture was heated to 270° F. atwhich time a mixture of 911 g of the resin from Example XXXIX, 132 giso-butylmethacrylate, 26 g hydroxyethyl acrylate, 27 g styrene, 3.6 gt-butylperbenzoate, and 15 g acrylic acid was added dropwise over aperiod of 5 hours. The mixture was postreacted at 270° F. for 2 hours,the solvent brought to reflux, and 500 g xylene stripped off to affordthe final resin with a J viscosity at 65% non-volatiles.

EXAMPLES XLI-XLVIII

One and two component flexible clear coat compositions (the term"flexible" refering to the cured coating) suitable for use in abase/clear automotive coating system were formulated according to thecompositions shown in Table D. The order of addition was as follows. Inthe case of one component coatings formulated with Cymel 1130(trademark; American Cyanamid Co.; alkylated melamine crosslinkingagent), the resin was mixed with n-butylacetate, aUV-stabilizer/absorber package, butyl-acrylate, methyl amyl ketone, andTetralin. The mixture was added to a premixed solution of Cymel 1130,acid catalyst, cellosolve acetate, and xylene. The viscosity of thecoating formulation was adjusted to 20 sec. #4 Ford Cup (80° F.) with amixture of xylene and 2-ethylhexanol. In the case of two componentcoatings formulated with an organic polyisocyanate, the resin was mixedwith n-butylacetate, a UV-stabilizer/absorber package, butyl acrylate,methyl amyl ketone, and Tetralin. To this mixture the polyisocyanate,predissolved in xylene and cellosolve acetate, was added just beforespraying. The viscosity of the coating formulation was adjusted to 20sec #4 Ford Cup (80° F.) with xylene. Bonderite steel panels and RIMpanels were sprayed first with a high solids base coat and the clearcoat was applied wet on wet. The panels were baked at 250° F. for 30minutes to yield smooth, tough films with excellent flexibility andexcellent chemical and oxidative stability.

                                      TABLE D                                     __________________________________________________________________________    CLEARCOAT COMPOSITIONS                                                                        EXAMPLE                                                       COMPOSITION     XLI                                                                              XLII                                                                             XLIII                                                                             XLIV                                                                              XLV                                                                              XLVI                                                                              XLVII                                                                             XLVIII                               __________________________________________________________________________    Resin of Example XXXIII                                                                       53.9          53.9                                            Resin of Example XXXV                                                                            64.5          64.5                                         Resin of Example XXXVII                                                                             62.6           62.6                                     Resin of Example XL       65.5           65.5                                 n-butyl acetate 7.2                                                                              7.2                                                                              7.2 7.2 7.2                                                                              7.2 7.2 7.2                                  UV stabilizer/absorber package.sup.1                                                          13.8                                                                             13.8                                                                             13.8                                                                              13.8                                                                              13.8                                                                             13.8                                                                              13.8                                                                              13.8                                 polybutyl acrylate                                                                            0.96                                                                             0.96                                                                             0.96                                                                              0.96                                                                              0.96                                                                             0.96                                                                              0.96                                                                              0.96                                 methyl amyl ketone                                                                            18.2                                                                             18.2                                                                             18.2                                                                              18.2                                                                              18.2                                                                             18.2                                                                              18.2                                                                              18.2                                 Tetralin.sup.2  12 12 12  12  12 12  12  12                                   xylene          10 10 10  10  14 14  14  14                                   cellosolve acetate                                                                            1  1  1   1   1  1   1   1                                    Acid catalyst.sup.3                                                                           1.2                                                                              1.2                                                                              1.2 1.2                                                 Cymel 1130.sup.4                                                                              14.1                                                                             14.1                                                                             14.1                                                                              14.1                                                Desmodur N-3390.sup.5         22.8                                                                             22.8                                                                              22.8                                                                              22.8                                 __________________________________________________________________________     .sup.1 Solution of 25 parts TIN 079L, 8 parts TIN 900, 7 parts TIN 328        (trademarks; CibaGeigy Co.) and 60 parts xylene.                              .sup.2 1,2,3,4tetrahydronaphthalene.                                          .sup.3 Paratoluene sulfonic acid, 40% solution in butanol.                    .sup.4 Trademark; American Cyanamid Company; alkylated melamine               crosslinking agent.                                                           .sup.5 Trademark; Mobay Chemical Corporation; polyisocyanate crosslinking     agent.                                                                   

EXAMPLES XLIX-LI

One component, high solids, flexible base coat compositions suitable foruse in a base/clear automotive coating system were formulated accordingto the compositions shown in Table E. The components were added in theorder listed and in the manner, generally, described for one componentclear coat compositions of the preceding examples. The compositions werereduced to 20 sec #4 Ford Cup (80° F.) with methyl amyl ketone.

                  TABLE E                                                         ______________________________________                                        BASECOAT COMPOSITIONS                                                                       EXAMPLE                                                         COMPOSITION     XLIX       L       LI                                         ______________________________________                                        Resin of Example XXXV                                                                         125                                                           Resin of Example XXXVII    125                                                Resin of Example XL                125                                        Spenlite LO6-30S.sup.1                                                                        19.2       19.2    19.2                                       Cymel 1130.sup.2                                                                              52.4       52.4    52.4                                       Cymel 1161.sup.2                                                                              35.2       35.2    35.2                                       Tinuvin-328.sup.3                                                                             9.6        9.6     9.6                                        para-toluene sulfonic                                                                         2.0        2.0     2.0                                        acid solution (40%                                                            in butanol)                                                                   5000-AR.sup.4   123        123     123                                        Microgel flow control                                                                         96         96      96                                         additive.sup.5                                                                Esterdiol-204.sup.6                                                                           46         46      46                                         cellosolve acetate                                                                            19.2       19.2    19.2                                       aluminum stearate                                                                             96         96      96                                         xylene          15.4       15.4    15.4                                       isopropyl alcohol                                                                             15.4.      15.4    15.4                                       ______________________________________                                         .sup.1 Trademark; SpencerKellog, Buffalo, N.Y.; linear polyurethane           modifying agent for aluminum pigment orientation.                             .sup.2 Trademark; American Cyanamid Co., Wayne, N.J.; alkylated melamine      crosslinking agent.                                                           .sup.3 Trademark; CibaGeigy; U.V. absorber.                                   .sup.4 Trademark; Silberline Co., Lansford, PA.; aluminum paste.              .sup.5 Prepared according to Examples 1-3 of U.S. Pat. No. 4,425,450.         .sup.6 Trademark; Union Carbide Corp.; diol.                             

EXAMPLE LII

A millbase was prepared by grinding in a ball mill the followingmixture:

    ______________________________________                                        Composition        Parts                                                      ______________________________________                                        Resin of Example XL                                                                              107                                                        Anti-Terra U       19                                                         Barium sulfate     547                                                        TiO.sub.2          103                                                        Carbon black       4                                                          Xylene             150                                                        Toluene            50                                                         ______________________________________                                    

A two component primer coating composition was formulated by mixing thefollowing components:

    ______________________________________                                        Composition        Parts                                                      ______________________________________                                        Millbase (above)   746                                                        Resin of Example XL                                                                              458                                                        Desmodur L-2291A.sup.1                                                                           150                                                        Methyl amyl ketone 50                                                         ______________________________________                                         .sup.1 Trademark; Mobay Chemical Corp.; polyisocyanate crosslinking agent                                                                              

The above composition was mixed (within 5 minutes), reduced to 19 sec #4Ford Cup (80° F.) and sprayed over both Bonderite steel panels andplastic panels. The panels were baked for 30 minutes at 250° F. to givesmooth, tough films with excellent solvent resistance (20+ MEK rubs).

EXAMPLES LIII-LIV

Two component enamel coatings were formulated according to thecompositions shown in Table F. The order of addition was as follows:First the resin was mixed with the flow control additive, celluloseacetate butyrate and 2-ethyl hexyl acetate. Subsequently, the aluminumpaste was predissolved in 15 parts of butyl cellosolve acetate and addedto the mixture. After the aluminum paste was dispersed, the rest of thebutyl cellosolve acetate was added. To this mixture the polyisocyanatecrosslinking agent, predissolved in 30 parts of methyl amyl ketone, wasadded just before spraying the coating. The viscosity of the paint wasadjusted to 20 sec #∝Ford Cup (80° F.) with methyl amyl ketone.Bonderite steel panels and plastic panels were sprayed and baked for 30minutes at 250° F. to give smoth, tough films with excellent flexibilityand MEK resistance.

                  TABLE F                                                         ______________________________________                                        Composition          LIII    LIV                                              ______________________________________                                        Resin of Example XL  212     212                                              Microgel flow control additive.sup.1                                                               5       5                                                Cellosolve acetate Butyrate.sup.2                                                                  2       2                                                2-Ethyl hexyl acetate                                                                              15      15                                               Aluminum paste.sup.3 9       9                                                Butyl cellosolve acetate                                                                           50      50                                               Desmodur L-2291.sup.4                                                                              71      107                                              Desmodur Z-4370.sup.4        30                                               Methyl amyl ketone   30      30                                               ______________________________________                                         .sup.1 Prepared according to Examples 1-3 of U.S. Pat. No. 4,425,450.         .sup.2 Eastman Chemical Co.; CAB 3810.1 (trademark).                          .sup.3 Silberline Co.,; 8199AR (trademark).                                   .sup.4 Trademark; Mobay Chemical Corp.; polyisocyanate crosslinking agent                                                                              

I claim:
 1. Hydroxy functional carbon-carbon double bond-bearingbranched polysiloxane macromer consisting of the reaction product ofreactants comprising (i) epoxy monomer having the formula: ##STR7##wherein R is hydrogen or C1 to about C7 alkyl, and R' is C1 to about C7alkyl or COO(CH₂)_(n), n being 0 to about 7, with (ii) hydroxyfunctional polysiloxane reactant having about 0-10 urethane groups permolecule consisting of oligomeric straight chain polysiloxane having anumber average molecular weight between about 1,000 and about 10,000 anda hydroxyl number between about 30 and about
 300. 2. The hydroxyfunctional carbon-carbon double bond-bearing branched polysiloxanemacromer of claim 1, wherein said epoxy monomer consists of a glycidylacrylate, glycidyl methacrylate or a mixture thereof.
 3. A solvent basedflexible coating composition, useful as an automotive coating on metaland plastic substrates, comprising:(A) hydroxy functional polysiloxanegraft copolymer of number average molecular weight between about 1,000and about 15,000, having a hydroxyl number between about 30 and about300, and being the reaction product of carbon-carbon doublebond-reactive monoethylenically unsaturated monomer with hydroxyfunctional carbon-carbon double bond-bearing branched polysiloxanemacromer, under free radical polymerization reaction conditions, saidmonomer bearing substantially no functionality which is substantiallyreactive with hydroxy functionality of said macromer under said reactionconditions, which macromer is the reaction product of (i) epoxy monomerhaving the formula: ##STR8## wherein R is hydrogen or C1 to about C7alkyl, and R' is C1 to about C7 alkyl or COO(CH₂)_(n), n being 0 toabout 7, with (ii) hydroxy functional polysiloxane reactant having about0-10 urethane groups per molecule comprising oligomeric straight chainpolysiloxane having a number average molecular weight between about1,000 and about 10,000 and hydroxyl number between about 30 and about300; and (B) polyfunctional, hydroxy-reactive crosslinking agentselected from aminoplast crosslinking agent, polyisocyanate crosslinkingagent, blocked polyisocyanate crosslinking agent comprising at least twoioscyanate groups blocked by reaction with active hydrogen bearingblocking agent, (and) or (compatible) mixture of any of them, saidcrosslinking agent being included in an amount sufficient to provide, ata cure temperature of said composition, between about 0.5 and about 1.6hydroxy reactive groups per hydroxy group contributed by said hydroxyfunctional polysiloxane graft copolymer.
 4. The coating composition ofclaim 3 in which the epoxy monomer of the macromer consists of glycidylacrylate, glycidyl methacrylate or a mixture thereof.
 5. The coatingcomposition of claim 3 in which the crosslinking agent is an alkylatedmelamine crosslinking agent.